Add missing gmock dependency

Author: christophfroehlich

joint_trajectory_controller_plugins/package.xml

@@ -15,10 +15,11 @@
   <depend>pluginlib</depend>
   <depend>trajectory_msgs</depend>
 
+  <test_depend>ament_cmake_gmock</test_depend>
   <test_depend>ament_lint_auto</test_depend>
   <test_depend>ament_lint_common</test_depend>
 
   <export>
     <build_type>ament_cmake</build_type>
   </export>
-</package>
+</package>